Apple has revealed that an independent non-profit labour group has launched a major investigation into the working conditions at a number of its suppliers, including the controversial Chinese firm Foxconn.

Apple has revealed that an independent non-profit labour group has launched a major investigation into the working conditions at a number of its suppliers, including the controversial Chinese firm Foxconn.

The Fair Labor Association (FLA) began its investigation at Foxconn's factory in Shenzhen, better known as “Foxconn City.” Foxconn is under particular scrutiny after a wave of suicides and attempted suicides, including 14 deaths in 2010.

Suicide is not the only worry for Apple, as Foxconn also came under the spotlight again last year after an explosion at its Chengdu factory killed three employees. The FLA is also investigating that facility.

Foxconn assembles both the iPhone and iPad ranges, two of Apple's most popular products, which makes Foxconn's widely reported poor working conditions reflect badly on the Cupertino, California-based company.

Apple has attempted to rectify the problem, which is increasingly tarnishing its image, by launching several investigations of its own. Last month it released details of an audit of its entire supply chain, a significant move to enhance transparency.

Other Apple suppliers, such as Quanta and Pegatron, will be subject to investigations by the FLA later this year.

Apple's CEO, Tim Cook, who took over from Steve Jobs last year, said that the inspections that are now underway are “unprecedented … both in scale and scope.”